C# Signatures:

[DllImport("oleaut32.dll")]
static extern int RegisterTypeLib(ITypeLib ptlib,
   [MarshalAs(UnmanagedType.BStr)] string szFullPath,
   [MarshalAs(UnmanagedType.BStr)] string szHelpDir);

[DllImport("oleaut32.dll", PreserveSig=false)]
static extern void RegisterTypeLib(ITypeLib ptlib,
   [MarshalAs(UnmanagedType.BStr)] string szFullPath,
   [MarshalAs(UnmanagedType.BStr)] string szHelpDir);

VB Signature:

Declare Function RegisterTypeLib Lib "oleaut32.dll" (TODO) As TODO

User-Defined Types:

For the ITypeLib parameter, you can use System.Runtime.InteropServices.UCOMITypeLib, already defined in mscorlib.dll. Note that in v2.0 (Whidbey) of the .NET Framework, this interface has been deprecated in favor of System.Runtime.InteropServices.ComTypes.ITypeLib.

Notes:

The first signature returns the raw HRESULT. The second signature throws an exception when a failure HRESULT is returned.

Tips & Tricks:

Please add some!

Sample Code:

Please add some!

Alternative Managed API:

Do you know one? Please contribute it!